Abstract
Cylindrical enamel and dentin specimens, 0.8-1.0mm in diameter and 0.8-2.2mm in length, were prepared from freshly extracted third molars from teen-age females.Improved methods of preparing specimens of hard tooth tissues using a hollow drill made of pure copper with aluminium oxide paste as the abrasions at a rotation speed of 2, 000rpm and a load of IN(100gf)have been developed for the determination of proportional limit, yield strength, crushing strength, modulus of elasticity, and contraction.Specimens were prepared from different regions in the same teeth and different orientations of the structure, and were compressed at a rate of 0.1mm per minute.The following results were obtained.1.The compressive properties of enamel were affected significantly by the orientation of the specimens, but those of dentin were not affected.2.When the load parallel to the long axis of the enamel rod was applied, the values of compressive properties were at the minimum.When the load was applied through the head and the tail of the key-holl unit of the rod, the values of compressive properties were intermediate, and when the load was perpendicular to the axis through the head and the tail, the maximum values were obtained.3.Compressive yield strength of enamel could not be measured, but crushing strength was 270-440MPa.4.Compressive yield strength of dentin was 210-220MPa.
